A known variable valve timing control device favorably includes a driven side rotation member which is formed with a lightweight material which has small rotation inertia in order to easily change a relative rotational phase of the driven side rotation member relative to a driving side rotation member. Therefore, the driven side rotation member is generally made from a low strength material, for example, an aluminum material. On the other hand, a camshaft connected to the driven side rotation member is generally made from a high-strength material, for example, an iron material. Thus, a gap is easily formed at an interface between the driven side rotation member and the camshaft due to a difference between a coefficient of linear expansion of the driven side rotation member and a coefficient of linear expansion of the camshaft. Along with that, the driven side rotation member may be easily damaged because the high-strength camshaft is directly in contact with the low-strength driven side rotation member.
Especially, in a case where a flow path of the operation fluid which changes a relative rotational phase of the driven side rotation member relative to the driving side rotation member extends over the driven side rotation member and the camshaft, and the gap is generated at the interface of the driven side rotation member and the camshaft, the relative rotational phase cannot be changed precisely at the right time, or proper timing because of the leakage of the operation fluid via the gap.
A known variable valve timing control device is disclosed in JP2012-57578A (hereinafter referred to as Patent reference 1). The variable valve timing control device disclosed in Patent reference 1 is provided with a driving side rotation member (housing), a driven side rotation member (inner rotor), a fluid pressure chamber defined between the driving side rotation member and the driven side rotation member, and a control valve controlling the supplying and draining of the operation fluid to and from the fluid pressure chamber in order to change the relative rotational phase of the driven side rotation member relative to the driving side rotation member between a most advanced angle chamber and a most retarded angle phase. The variable valve timing control device further includes an intermediate member which is positioned inwardly of the driven side rotation member between the driven side rotation member and a camshaft and includes the control valve inwardly of the intermediate member. The driven side rotation member is made from an aluminum material, whereas the intermediate member is made from an iron material.
According to the variable valve timing control device disclosed in Patent reference 1, because the variable valve timing control device includes the intermediate member which is positioned inwardly of the driven side rotation member between the driven side rotation member and the camshaft, the driven side rotation member made from the aluminum material does not come in contact with the camshaft. Thus, in a case where the camshaft is made from a high-strength material, the driven side rotation member made from the aluminum material may be prevented from being damaged. Further, because the intermediate member is made from the iron material which includes a coefficient of linear expansion that is close to a coefficient of linear expansion of the camshaft which is made from the high-strength material, the gap is not generated at the interface of the intermediate member and the camshaft. Accordingly, in a case where the flow path of the operation fluid extends over the intermediate member and the camshaft, the relative rotational phase can be changed precisely at the right time, or proper timing because the operation fluid does not leak easily.
According to the variable valve timing control device disclosed in Patent reference 1, the intermediate member is inserted from an end of the driven side rotation member to be positioned between an inner circumference of the driven side rotation member and an outer circumference of the camshaft. Thus, after mounting the driven side rotation member and the intermediate member to the driving side rotation member, the intermediate member may easily come out of the inner circumference of the driven side rotation member when the camshaft is mounted to the variable valve timing control device. Accordingly, the mounting process of the variable valve timing control device may be complicated.
A need thus exists for a variable valve timing control device which is not susceptible to the drawback mentioned above.